1. Field of the Invention
The present invention relates generally to mechanical stokers, and particularly to an improved construction of a rotary grate continuous ash discharge stoker in which the rotary grate includes an inclined rotating outer ring. This improved construction may be used in either an overfeed or an underfeed mechanical stoker design. Numerous other possible designs and combinations thereof are includable in the scope of the invention.
2. Description of the Prior Art
Rotary continuous ash discharge stokers are known which have a substantially horizontally circular grate which is designed to support burning fuel as it distributes the fuel from the feed point over the entire grate, and at the same time automatically removes the ash therefrom. Another known rotary stoker employs a pair of concentric rotating grates in stepped relation to one another; the outer grate disposed above the inner grate. It is also known to provide for the controlled admission of air for combustion of the fuel in a controlled and efficient manner. In particular, the assignee of the present invention has developed a continuous ash discharge rotary stoker which is described in the U.S. Pat. No. 4,437,452, issued to David C. Reschly on Mar. 20, 1984, based on application Ser. No. 482,015 and entitled "Rotary Continuous Ash Discharge Stoker". Said application was filed Apr. 11, 1983 and is a continuation of application Ser. No. 62,327 filed July 31, 1979, now abandoned. In that Patent is described a rotary stoker in which the upper grate surface consisted of two zones, a central stationary section and an outer rotating section or ring. The central section is inclined and provides a main air admitting zone. The outer rotating ring is generally horizontal and serves to distribute the fuel in the furnace with the aid of a stationary spreader arm. Air is also admissible through the rotating ring to aid combustion and the burned out ash from the furnace is removed at the outer periphery with the aid of a stationary ash plow. Said invention thus provides a stoker which is capable of continuous operation (although it is also possible to halt the continuous operation by stopping the rotating ring and ceasing to feed fuel).
In addition to providing for the continuous burning of fuel and removal of ash, the Reschly invention provides a wide latitude of control over the admission of air, both below the fuel supported grate and above the grate. Separate wind boxes or air plenums, receptive of pressurized air, and separately controllable, allow the furnace or boiler operator to optimize combustion by admitting air in the precise zone or zones as needed.
While the above-described stoker design has proven to be quite advantageous, further improvements in the design to promote more even and complete combustion and smoother, more trouble free ash removal are always desirable.